Nano-sensors for oil and gas reservoir characterization

Abstract

Enhanced oil recovery becomes increasingly important in satisfying the growing demand for fossil fuel. The efficiency of secondary recovery processes like water flooding is however largely influenced by the rock characteristics, fluid characteristics, chemistry and physics. For development of the full potential of secondary oil recovery, it remains a challenge to obtain sufficient knowledge about the reservoir conditions. The present invention provides a novel water-dispersed, nano-sensor composition based on. InP / ZnS quantum dots (“QDs”) and atomic silver clusters, which exhibit a bright visible fluorescence combined with dedicated sensor functionalities. The QD and silver nano-sensors were tested in simulated reservoir conditions to determine their selected functionality to these reservoir conditions. The developed nano-sensors showed improved sensor functionalities towards pH, temperature, and subterranean reservoir rock, such, as clay or limestone.

Description

[0001]This application claims priority to U.S. Provisional Patent Application Ser. No. 61 / 624,346 filed Apr. 15, 2012, which is hereby incorporated by reference herein.BACKGROUND AND SUMMARY[0002]As a result of the ever expanding demand for energy, the world's easily accessible oil reserves become swiftly depleted. The oil and gas industry today has a typical recovery of hydrocarbons with value of 30-40%,1,2 which indicates that the majority of the existing oil remains trapped in the pores of the oil bearing porous media. An increase in recovery efficiency (up to 60-80%)1 will therefore be a key factor for meeting the increasing energy demands. To this end, there is a need for new and more sophisticated mapping and production techniques.[0003]Injection of water, also referred to as water flooding,3 is commonly applied to produce so-called secondary oil, resulting in an increase of the total recovery efficiency up to 50%.4 The recovery results of a water flooding process is largely i...

AI Technical Summary

Benefits of technology

[0008]Another and relative new type of “nano” particles are the so-called noble metal clusters. Their bright optical behavior, which is size-tunable, is to a certain extent comparable to that of QDs.17 Their inert inorganic nature together with their relatively high chemical stability and solution process ability makes these noble metal clusters an interesting material to combine with the earlier discussed QDs in a mixed sensor for reservoir imaging. Water-dispersed nano-sensors are compatible with the commonly applied technique of water flooding and therefore an ideal starting point, as its infrastructure is readily available throughout the oil and gas industry for enhanced oil recovery.3 Extended information about the specific chemical and physical conditions within the reservoir is beneficial to optimize secondary oil production.

[0011]QDs and silver clusters are described herein as a class of materials for applications as luminescent probes with dedicated sensor functionalities for reservoir imaging, exhibiting stability and a significant freedom for surface chemistry.

Problems solved by technology

As a result of the ever expanding demand for energy, the world's easily accessible oil reserves become swiftly depleted.

The limitation of the commonly applied isotope tracers is that they primarily provide information on flow characteristics, and often do not possess any physical and chemical sensor functionality.10 In addition, a significant number of reported tracers consist of either toxic compounds or radioactive nuclides.8,9 This limits their use due to health, safety, environmental, and legislation issues.

The challenging reservoir conditions (e.g., high salinity, high pH, and temperature) have often been found as the limiting factor on the stability of fluorescent materials for reservoir imaging.

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